It is highly desirable to provide alternatives to conventional sprinkler irrigation systems and the like since such systems tent to be very water and power intensive yet cannot achieve maximum plant growth rate. It is highly desirable to utilize trickle irrigation in place of conventional sprinkler systems and the like; in trickle irrigation water is applied on a slow steady basis to the plant's root zones to replace water which is lost by evaporation from the soil and transpiration by the plant. Trickle irrigation can result in a great reduction in the amount of water used, a reduction in weed growth since the water is applied proximate the root zone and not on a broad basis, can be used in a wide variety of terrains and soil types, and can spur more rapid growth and earlier production of young trees and plants.
While trickle irrigation systems are highly desirably, in the past there have been practical problems associated with conventional trickle irrigation systems. Even when used with clean source water, conventional trickle irrigation systems are relatively energy intensive and have a relatively short useful life. When used with very silty water, conventional trickle irrigation systems become clogged very quickly, require a great deal of labor for maintaining the system in operation, require sophisticated filtration systems that also consume energy in the cleaning thereof, and do not have the capability of delivering the predetermined amount of water to each discharge point with a reasonable, measured accuracy.
According to the present invention a trickle irrigation system, and method of utilization thereof, are provided that overcome most of the problems inherent in conventional trickle irrigation systems, while allowing all of the advantages associated with trickle irrigation to be achieved. The system according to the present invention operates at low pressure (10 psi maximum) using inexpensive rigid thin-walled pipe (e.g., PVC pipe) of relatively large diameter. The system is highly energy efficient, having a maximum power consumption of 0.05 hp/acre, and is capable of delivering a specified quantity of water to each discharge point with a deviation of only .+-.20%. The system is capable of handling even very silty, trashy, dirty water, no sophisticated filtration systems are provided, and the entire system may be periodically flushed with an absolute minimal amount of labor input. The system is durable, having a minimum life expectancy of 10 years, requires little labor for maintenance, and can be readily inspected by an operator on a motor vehicle and easily maintained in the field.
According to one aspect of the present invention, a low pressure, trickle irrigation system is provided comprising a buried, generally horizontal main line adapted to be connected to a source of water, and a plurality of open-top emitters in liquid communication with the main line. The emitters each extend generally vertically a predetermined distance E above the ground with the discharge points of all emitters having substantially the same height above sea level (taking into account head losses). An open-top flush pipe is in fluid communication with the emitters and extends generally vertically a predetermined distance L above the ground, the distance L being significantly less than the lowest distance E. Capping means are provided for removably capping the flush pipe so that no water may flow through the open top of the flush pipe when in place, and water may flow through the open top when not in place.
According to another aspect of the present invention a low pressure, trickle irrigation system is provided comprising a head control means for controlling the head of water providing pressure to the system; a water inlet to the head control means and pumping means operatively connected to the water inlet; and a buried, generally horizontal main line operatively connected to the bottom of the head control means, the main line of relatively thin-wall rigid large diameter pipe (e.g., PVC pipe). A plurality of lateral lines are provided above the main line, directly connected to the main line and buried underground and extending generally horizontally and generally perpendicular to the main line. The lateral lines also are of a thin walled rigid pipe (e.g., PVC pipe) with a diameter smaller than that of the main line. A plurality of open-top emitters are directly connected to each of the lateral lines and extend generally upwardly therefrom so that the discharge points thereof are all above ground and at substantially the same height above sea level. Preferably the open top of each emitter includes a V-shaped notch formed in the emitter pipe wall providing a water discharge point through which notch the water trickles, and a dust cover may be provided on top of each of the emitters. The system is very useful in irrigating a plurality of rows of trees. In that case, each lateral line extends parallel to the rows of trees intermediate two rows so that the emitters associated with each lateral line water two tree rows, each emitter disposed between trees; and each lateral line is spaced from adjacent other lateral lines a distance approximately equal to the width of two rows of trees.
According to another aspect of the present invention, a holding tank for a low pressure irrigation system is provided, the tank comprising tank walls, a removal lid, and a flexible mesh having peripheral portions thereof disposed between the removal lid and the tank walls and having a central portion of the mesh loosely hanging in the tank interior. The flexible mesh may be of any open weave non-biodegradable material such as a woven glass having a open weave of about 5 to 10 mesh/in. A liquid inlet extends into a top portion of the tank and discharges into the interior volume defined between the flexible mesh and tank lid, and an outlet from the tank is located on the opposite side of the flexible mesh from the tank inlet. Valve means are provided in the tank outlet for controlling the level of liquid in the tank so that it is above the central portion of the flexible mesh but below the peripheral portions thereof.
The invention also contemplates a method of irrigating a land area. The method includes the following steps: Disposing an irrigation system, including a head control device with an underground main line extending therefrom and emitters operatively connected to the main line and extending vertically to an open-top above ground level, in the land area. Sizing the pipes defining the irrigation system and controlling the head control device so that the maximum pressure in the system is about 10 psi, and so that the pressure is zero head plus the head necessary to supply water to the open tops of the emitters. And, supplying water from a source to the head control device so that the power consumption of the entire system is a maximum of about 0.05 hp/acre of land irrigated thereby. The irrigating water supply may be heavily silted with the only filtration provided being prior to discharge of the water into the head control device utilizing a filter having a maximum of 10 mesh/in. By removing caps from flush pipe associated with each group of emitters, flushing of the entire system is greater facilitated so that the method may be practiced indefinitely without clogging of the system and with a mimimal of labor input.
It is the primary object of the present invention to provide a practical, effective, low energy consumption, low pressure, trickle irrigation system and irrigating method. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.